Levels of a type of adult stem cell in the bloodstream may indicate a person's risk of developing cardiovascular disease, according to a study supported by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health.

The study looked at the blood level of endothelial progenitor cells, which are made in the bone marrow and may help the body repair damage to blood vessels. Scientists from NHLBI and Emory University Hospital in Atlanta, GA, found that cardiovascular disease risk was higher in persons with fewer endothelial progenitor cells. The cells of those at higher risk also aged faster than those at lower risk, as determined by the Framingham Heart Study risk factor score, a standard measurement of cardiovascular risk. Additionally, the study found that blood vessels were much less likely to dilate and relax appropriately in persons with low levels of the cells.

The two main forms of cardiovascular disease are heart disease and stroke. Standard heart disease risk factors are age, family history of early heart disease, smoking, high blood pressure, high blood cholesterol, overweight/obesity, physical inactivity, and diabetes.

"Past research on cardiovascular disease has often focused on what causes the damage to the blood vessels," said Dr. Toren Finkel, chief of NHLBI's Cardiology Branch and coauthor of the study. "We looked at the other part of the equation: How does the body repair damaged blood vessels? What does that tell us about the cause of the disease?

"We believe that these endothelial progenitor cells patch damaged sites in blood vessel walls," he continued. "When the cells start to run out, cardiovascular disease worsens. We don't yet know what causes their depletion but it may be related to the fact that the risk of cardiovascular disease increases as people age. For instance, the cells may be used up repairing damage done by other risk factors or those risk factors could directly affect the survival of the endothelial cells themselves.

"Much more research needs to be done to better understand this finding," Finkel added. "But it's possible that, some day, doctors may be able to test a person's risk of cardiovascular disease by taking a blood sample and measuring these cells. If the level is too low, an injection of endothelial cells might boost the body's ability to repair itself and prevent more blood vessel damage."